Water heating system



March 2, 1943- c. M. osTERHELD 2,312,772

WATER HEATING SYSTEM Filed June 14, 1941 A TT@ p/VEY Patented Mar. A2,1943 WATER HEATING SYSTEM Clark M. Osterheld, Stoughton, Wis., assignerto McGraw Electric Company, Elgin, Ill., a corporation of DelawareApplication June 14, 1941, Serial No. 398,094

4 Claims. (lCl. 21S-39) My invention relates to electric temperaturecontrol systems and particularly to water heating control Systems.

An object oi my invention is to provide a relatively simple all-daywater heating system.

Another object of my invention is to provide a water heating controlsystem embodying thermal means subject to tank water temperature at apredetermined point or height of the tank to vary the amount of electricenergy translated into heat for the water in the tank.

Other objects of my invention will either be apparent from a descriptionof my invention as embodied in several modifications or will be pointedout in the course of such description and set forth in the appendedclaims.

In the drawing:

Figure l is a schematic diagram of connections embodying my inventionshown as applied to an ordinary domestic hot water tank, which is showngenerally only, and,

` Fig. 2 is a view similar'to Fig. l showing a modified system ofcontrol.

Since the system embodying my invention is particularly applicable toand useful in the control of electric heaters used on ordinary domestichot water tanks, have elected to show, schematically only, a hot watertank I l which is to be understood as being provided with a cold waterinlet pipe, preferably at the bottom of the tank, and with a hot wateroutlet pipe at the top of the tank. The tank may also be provided withthe usual layer of heat insulating material and with an outer protectivecasing for such material. However, since my invention has nothing to dowith these details. I have shown the tank generally only.

Referring to Fig. 1, an electric heater comprises two sections I3 and I5and I may make the resistance of these two sections the same or I maymake the resistance of section I3 greater than that of section I5 sothat when section I5 is energized separately, the amount of electricalenergy translated into heat in section I5 will be greater than ifsection I3 were energized alone. I prefer to apply these two sections ofthe heater to the tank near the lower end thereof, as shown in Fig. l ofthe drawing.

I provide a lower main thermal heater control switch I1 here shown asembodying a tubular member i 9 so secured to the wall of tank II as toextend into the tank in a fluid-tight manner. An expansion rod 2i ispositioned within the tubular member I9 and extends outwardly beyond theouter surface of the wall of tank II engaging a contact or switch arm23. This contact arm is adapted to engage with or be disengaged from afixed contact member 25. When tubular member I9 is subject to coldwater, switch arm 23 will be in engagement with xed contact member 25but if tubular member I8 is surrounded by and subject to hot water, theexpanded rod ZI will have moved the switch arm 23 out of engagement withfixed contact member 25 to thereby interrupt a circuit controlled bythis switch.

I provide an auxiliary thermal switch 21 which is preferably located atan intermediate point or height of the tank iI and for illustrativepurposes it may be positioned at about one-half of the height of thetank or even at about twothirds of the height of the tank from thebottom. Switch 21 includes a tubular contact member 29 secured to thewall of the tank in a duid-tight manner to be positioned within the tankand has located therein an expansion rod 3| adapted to move a Contact orswitch arm 33. The movable end of arm 33 is adapted to engage either oneof two xed contact members 35 and 31, it being understood that thedesign, construction and ad- J'ustment of the thermal switch 21 is suchthat the free end of arm 33 is in engagement with either contact member35 or with contact member 31, but has no intermediate position. I mayuse any of the present types of two-operative position switches now onthe market to obtain this result but have not shown any details thereofsince they do not form any part of my present invention.

I provide two supply circuit conductors 39 and 4I, supply circuitconductor 39 being connected to the plvotally mounted end oi switch arm33. Fixed contact member 35 is connected by a conductor 43 with oneterminal of each of the heater sections I3 and I5. The other end ofheater section I3 is connected by a conductor 45 with the xed pivotalend of switch arm 23. Contact member 25 is connected by a conductor l1with xed contact member 31. The other terminal of heater section i5 isconnected by a conductor 49 with the other supply circuit conductor It.

Let it be assumed that the tank H has just been lled with cold water andthat the supply circuit conductors 39 and 4I are connected to suitablesupply circuit of electric energy. The two thermal switches I1 and 21will be in substantially the position shown in Fig. 1 of the drawing, e.g., switch arm 23 will be in engage ment with fixed contact 25 andswitch arm 33 will be in engagement with fixed contact 35. An energizingcircuit through the heater will therefore be established substantiallyas follows: From supply circuitconductor 39 through engaged switch arm33 and contact 35, through conductor 43 and through heater section I5 toand throughconductor 49 to the other supply circuit conductor 4I. energywill therefore be translated into heat depending upon the resistance ofheater section I and since this heater section alone is connected incircuit, i'n this diagram of connections. it may be considered that arelatively large amount of electrical energy isr `translated into heatcausing the temperature of the waterin the tank to increase at arelatively rapid rate.

Let it now be assumed that the amount` of hot water in the tank hasincreased, because of the fiow of current for some time through ,heatersection I5 and attendant heating of the water', to such an extent thattubular member- 29 of the upper or auxiliary thermal switch issurrounded by hot water. When this occurs the expanded rod 3i will causemovement of switch arm 33 out of engagement with xed contact 35 and intoengagement with fixed contact 31 whereby a new circuit through theheater is provided, substantially as follows: From supply circuitconductor 39 to and through engaged switch arm 33 and contact 3l,through conductor 41 to and through engaged contact 25 and switch arm23, through conductor 45, through heater sections I3 and I5 connected inseries circuit with each other and from there through conductor 49 tothe other supply circuit conductor 4I. It will therefore be evident thatwhen a certain fractional part of the amount of water imthe tank hasbeen heated to a given temperatura the upper or auxiliary thermalswitchwill cause a lchange-over in the heating circuit whereby the twosections of the electric tank heater are connected in series cire cuitwith each other whereby the amount of electrical energy translated intoheat is greatly reduced. y

It is therefore evident that when the tank, at any time, contains arelatively small amount of `hot water, which may be considered to beless than that required for normal household needs and purposes, theamount of electrical energy translated into heat is relatively large butas soon as an amount of water in the tank sumcient for normal householdpurposes has been heated, the amount of electrical energy translatedinto heat and applied to the water in the tank is greatly reduced.

Referring now to Fig. 2 of the drawing, I have there illustrated amodied system embodying myinvention. I have shown a two-section heatercomprising sections 49 and 5i both sections being located near the lowerend of the tank II. For purposes of illustration I have shown a mainlower thermal switch 53 asincluding a ilexible bimetal bar 55 having oneend thereof mounted on suitable electric and heat conducting meanssubject to the temperature of the water in the lower part of the tankand adapted to engage with and be disengaged from a fixed contact member51. This main thermal heater control switch need not be of thetwo-operative position type since it is merely required to open thecircuit when substantially all of the Water in the tank is hot and Ihave shown a bimetal switch to illustrate that such a type of switch maybe used.

I provide an upper thermally actuable heater control switch 59 whichincludes a tubular member 3| substantially the same as tubular member Anamount of electrical hot water.

29 and located at an intermediate height of the tank which may be eitherat one-half height or at two-thirds height from the bottom of the tank.An expansion rod or bar 53 is adapted to pivotally move a contact orswitch arm 55 in accordance with the temperature of the water to whichthe tubular member 5I is subjected. An outer ilxed contact member 51 maybe engaged by switch arm 55 when the tubular member 3i is subject to Iprovide two inner xed contact members 59 and 'II spaced apart from ,eachother and adapted to be engaged by contact or switch arm 55 when tubularmember 5l is subject to cold water. Switch 59 is designed. constructed`and adjusted so that arm ,'55 is 'in engagement l lower main thermalheatercontrol switch. Contact member 1I is connected by a conductor 15fwith one terminal of heater section 5 I The other terminal of heatersection 5I is connected to one terminal of heater 'section 49 which twotervminals are connected bya conductorI 11 with supply circuit conductor4I.-- s

Let it be assumed that tank il as shown in Fig. 2 has justbeen filledwith cold water and that supply circuit conductors 39 and 4I areconnected to a suitable source of supply of electric energy. Bimetal bar55 will be in engagement with fixed contact member 51 and contact arm 55will be in engagement with xed contact members 58 and li.,y Thisestablishes an energizing circuit through the twosection heatersubstantially as follows: From supply'- circuit conductor 39 to andthrough engaged contact arm 55 and fixed contact member 59, throughconductor I3 to and through the engaged members of the lower mainthermal switch 53 and from fixed contact li through conductor i5 throughheater section 5I, and through heater section 49, through conductor I'Ito the other supply circuit conductor i It is evident that the twoheater sections are connected in parallel circuit relation with eachother. It is therefore evident that when the upper thermal heatercontrol switch 59 is subject to cold water, current will flow throughboth sections of the heater in parallel whereby a relatively largeamount of electrical energy will be translated into heat causing arelatively rapid heating up of the water in the tank II and itscollection at thellpper part of the tank, in a manner now Well known inthe art.

When the amount of hot water heated by current flowing from the twosections of the electric heater has increased to such an extent that theupper auxiliary thermal switch 59 is subject to hot water, contact arm55 will be moved out of engagement with fixed contact members 59 and 'iland into engagement with xed contact member 6l whereby anotherenergizing circuit through the heater is established substantially tothe other supply circuit conductor 4i. There-h fore, when the upper partof the tank is illed with hot water to such an extent that the upperauxiliary thermal switch 59 is surrounded by hot water, it will beeffective to establish a new energizing circuit through only one of thesections of the electric heater. Let it be assumed that the ohmicresistances of heater sections 49 and 5I are the same. Then it isevident that when only heater section 49 is energized as just abovedescribed, the amount of energy translated into heat will be onlyone-half of that which is translated into heat when both heater sectionsare energized in parallel circuit with each other, as is the case whenthe thermal heater control switch 59 is subject to cold water.

It will be noted that the lower thermal heater control switch I1 or 53is in circuit and in complete control when the tank is filled with hotwater and causes complete deenergization of the heater as soon as Athetank is full of hot water. In case of withdrawal of hot water, in smallquantities, the lower thermal switch will reclose and causereenergization of the heater at low watt input.

The two systems shown in the drawing and hereinbefore described willtherefore be eifective to translate a greater amount of electricalenergy into heat when the tank contains no or only a small amount of hotwater and it is, of course, to be understood, as has already beenhereinbefore stated, that this small amount of hot water is that whichwould be required to meet the normal demands or calls for hot water inthe course of the daylight hours.

While I have not shown any means for recording the amount of energy usedduring the daytime as distinguished from that used during socalledoff-peak hours, such means may be provided but are not shown since theyconstitute no part of my present invention.

Various other modifications may be made in the system embodying myinvention without departing from the spirit and scope thereof :and

I therefore desire that all such modifications as are clearly covered bythe appended claims shall be included as a part of my invention.

I claim as my invention:

1. A control system for a hot water tank having a plural-sectionelectric heater applied thereto near the lower end of the tank andadapted to heat water in only the lower end of the tank, comprising aswitching means having two operative positions, a thermal elementsubject to tank water temperature at a point substantially one-half ofthe height of the tank and adapted to move said switching means from oneto the other of its operative positions in accordance with its ambienttemperature, electric connections between the heater sections and theswitching means to cause the generation of a greater amount of heat bysaid heater when the upper half of the tank is filled with cold waterthan when the upper half of the tank is iilled with hot water and asecond thermally-operative switch subject to tank water temperature atthe lower end ot the tank for deenergizing said heater whensubstantially all of the water in the tank is hot.

2. A control system for a hot water tank having a two-section electricheater applied thereto near the bottom end of the tank and adapted toheat water in only the lower end of the tank, said system comprising athermally-actuable switch having two operative positions and subject totank water temperature near the upper end of the tank, electricconnections between the switch and the heater sections to bias thethermally-actuable switch into a first operative position to cause thegeneration of a predetermined amount of heat in the heater when theupper part of the tank is filled with cold water and to move thethermally-actuable switch into its second operative position to causethe generation of a smaller amount of heat in the heater when the upperpart of the tank is filled with hot water.

3. A control system for a domestic hot water` tank having a greaterheight than diameter and having a plural-section electric heater appliedthereto near the lower end of the tank adapted to heat water in only thelower end of the tank, comprising a switching means having two operativepositions, a thermal element subject to tank water temperature in theupper part of the tank, electric connections between the switching meansand the electric heater, the thermal element holding the switching meansin one of its operative positions to cause the genera.. tion of apredetermined amount of heat when subject to cold water and causing theswitching means to move into its other operative position to effect thegeneration of a lesser amount of heat when the thermal element issubject to hot water, a second switching Ameans comprising a thermalelement subject to tank water temperature in the lower end of the tankand normally holding the second switching means in heater energizingposition when subject to cold water and effective to move the secondswitching means to heater deenergizing position when the water in thelower end of the tank is hot.

4. A control systm for a domestic hot water tank having a greater heightthan diameter and having a plural-section electric heater appliedthereto near the lower end of the tank adapted to heat water in only thelower end of the tank, comprising a switching means having two operativepositions, a thermal element subject to tank water temperature in theupper part of the tank, electric connections between the switching meansand the electric heater, the thermal element holding the switching meansin one of its operative positions to energize one only of said heatersections when the thermal element is subject to cold water and causingthe switching means to move into its other operative position toenergize both said heater sections in series circuit with each otherwhen the thermal element is subject to hot water. j

CLARK M. OSTERHELD.

